1. Field Of The Invention
The present invention relates to the art of incandescent lampholder construction generally. In a more particular sense, the invention relates to the type of lampholder for incandescent lamps, having terminals to which current-carrying wires are separably connectable. In the present invention the terminals are of the type wherein insulation-displacing blades are extendible in paths disposed transversely of the lengths of the wire, for the purpose of displacing the wire insulation and making, as a consequence, direct contact with the metallic conductors of the wires. The invention is applicable both to lampholders or incandescent lamp sockets of the type having built-in switches, and sockets or lampholders known in the industry as lampholders of the keyless, that is, switchless type.
2. Description Of The Prior Art
Heretofore, lampholders, especially interiors, have most usually been provided with screw terminals. Such terminals, while quite efficient as a general proposition, tend to require excessive time in the connection of current-carrying wires to the lampholder. This is a matter of great significance in the lamp industry, since lampholders of the type disclosed in the present application are most usually mounted in table lamps, floor lamps, bridge lamps, and vanity lamps and indeed, in a seemingly limitless variety of appliances. The lampholders are normally sold in quantity to manufacturers of appliances of this type, for assembly into the finished product, and obviously in view of continually increasing costs of assembly labor, it is important to seek means whereby speeding up of the assembly of the wires with the lampholders can be achieved. Heretofore, little progress has been made in solving this problem, so far as lampholders of the so-called Edison-base type are concerned. In some instances, lampholders used for Christmas trees have utilized some types of insulation-piercing terminals for connecting a substantial number of said lampholders in parallel. However, when one seeks to embody so-called "quick-wire" terminals in Edison-base lampholders, many problems arise, since lampholders of this type must meet very stringent requirements so far as industry and Underwriters Labooratories standards are concerned. For example, typically lampholders of the type here under consideration carry ratings of 250 watts to 660 watts, 250 volts and must successfully pass exacting tests so far as voltage breakdown, heating, or the like are concerned.
So far as is known, the prior art has not as yet successfully provided a lampholder that can utilize and does utilize insulation-displacing terminals that will pass the exacting tests required for such lampholders, will be fully safe in that said terminals will be assured against movement out of their operative conductor-engaging postions, and will be adapted for swift and easy assembly with conductors without requirement of stripping the insulation therefrom - a practice which, it may be noted, is exceedingly expensive and time-consuming but which is absolutely necessary whenever terminals of the screw type are used.
For example, Underwriters Laboratories now requires that when the lampholder is an interior, the stripped ends of the conductors must be tinned to prevent stray wire ends from contacting a metal cap or shell in which the interior is mounted. This is a costly requirement for a portable lamp manufacturer, obviated by the invention which eliminates stripping and offers an extremely safe termination means.